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.375 Weatherby Magnum

History

Introduced in 1944, the .375 Weatherby is an improved version of the .375 Holland & Holland. In an attempt to increase the authority and efficiency of the .375 H&H Roy Weatherby blew out the case body dimensions of the H&H cartridge and added his signature double radius shoulder. The new dimensions gave, depending on case type, an average 10 grain increase in powder capacity.

The .375 Weatherby certainly produced more power than factory .375 H&H ammunition. Typical U.S manufactured 300 grain .375 H&H loads achieved a realistic 2470fps from 24” sporter barrels while the hot loaded 26” barreled .375 Weatherby achieved velocities of around 2750fps, a gain of 280fps.

Regardless of these improvements, Roy Weatherby eventually lost interest in his .375. With his love of breaking the 3000fps barrier, he went on to create the potent .378 Weatherby. The .378 Weatherby outshone the former cartridge and by 1960 the .375, though very useful in its own right, was made obsolete. Nevertheless, cases were easy enough to form for those already in ownership of .375 Weatherby rifles.

In 2001 the Weatherby arms company made the decision to revive their classic cartridge by once again producing factory ammunition.

 

Performance

Regardless of Roy Weatherby’s disassociation from this cartridge the .375 Weatherby, along with the basic .375 H&H Improved wildcat, are excellent cartridges suitable for a very wide range of game.

The .375 Weatherby produces fast emphatic kills on light game with appropriate bullet designs. Its increased velocity, at least out to moderate ranges, can also be used to help initiate expansion when using tougher bullets on lighter medium game.

The .375 Weatherby works extremely well on large bodied deer, bear and antelope species. Whether we choose the parent case or the Weatherby, .375 caliber projectiles driven at moderate to high velocities are simply outstanding when used on large bodied game weighing up to 450kg (1000lb).

As a heavy game cartridge I tend to agree with Roy Weatherby that there was room for more power and that the creation of the .378 was justified. While the recoil of the .375 Weatherby can be rather stout (especially when housed in the stylized Weatherby rifle), the power of this cartridge relative to its usage on heavy game should be considered mild. To say otherwise would place unrealistic expectations on it. By the same token the .375 Weatherby should not be under estimated.

In a custom rifle with a varmint style stock recoil tends to shunt the shooter around to some degree yet felt recoil is tolerable. Those who utilize a stock of sound design and practice regularly would find no need for a muzzle brake on this rifle. In anything less than a straight line stock the .375 Weatherby really needs some braking (partial braking fully acceptable) or weight within the barrel (11 to 12lb all up rifle weight) to lessen recoil and help enhance accuracy.
 

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Factory ammunition

Weatherby currently list just the one load for the .375, the 300 grain Nosler Partition at 2800fps. Sporting rifles with 26” barrels typically achieve 2780fps with this load while shorter 24” barreled rifles achieve around 2730fps. On light animals, and for game up to 320kg, the Partition is a fast killing bullet with very satisfying results. On heavy game the high velocity of the .375 Weatherby places the Partition under great stress during penetration at ranges under 125 yards. Hunters using this bullet on large heavy game at close range should not expect the Partition to pass through offside chest walls or shoulder bones on cross body shots. This bullet is adequate for game in the 450 range (1000lb) and non-dangerous game up to 600kg (1300lb).

As previously stated, the .375 Weatherby is able to utilize .375 H&H factory ammunition if need be, though this is not an advisable practice beyond fireforming operations. Velocity loss in the Weatherby chamber typically averages 100fps. Apart from the single Weatherby load, and H&H factory ammunition, the .375 must for all intents and purposes be considered today as a wildcat that requires handloading.
 

Hand loading

Brass for the .375 Weatherby can easily be formed using .300 Weatherby brass. Depending on the type of case used for fireforming, the .375 Weatherby case holds between 5 and 8 grains more powder than the .375 Ruger cases yet due to the more efficient case design of the latter velocities are for the most part identical when both are used in barrels of equal length.

Using powders in the IMR/ H4350 range the 26” barreled Weatherby produces 3075fps with 225-235 grain bullets, 3000fps with 250 grain bullets, 2950fps with 260 grain bullets, 2900fps with 270 grain bullets and 2750fps with 300 grain bullets.

Due to the fact that the .375 Weatherby produces velocities within 100fps of the .375 Ruger load and bullet performance is contained within that text. Further information on bullet performance can be found within the .375 H&H text and .375 caliber users are urged to study both articles and the different aspects that each cover.

 

Closing comments

The .375 Weatherby (and .375 H&H Improved) was and still remains a practical way to comfortably increase the power of the .375 H&H cartridge. And while the .375 Ruger produces similar performance the .375 Weatherby will continue to hold appeal among many hunters as a classic big game cartridge.

 

Suggested loads: .375 Weatherby Magnum

Barrel length: 26”

No

ID

 

Sectional Density

Ballistic Coefficient

Observed MV Fps

ME
Ft-lb’s

1

FL

Weatherby 300gr Partition

.305

.398

2780

5147

2

HL

235gr Speer, Barnes TSX,

Woodleigh

.239

.301

3075

4933

3

HL

250gr Sierra BTSP

.254

.375

3000

4995

4

HL

270gr Speer BTSP

.254

.429

2900

5041

5

HL

300gr Woodleigh PP

.305

.380

2750

5037

 

Suggested sight settings and bullet paths

 

 

 

 

1

Yards

100

244

282

300

325

350

 

 

Bt. path

+3

0

-3

-4.8

-7.8

-11.2

 

2

Yards

100

265

303

325

350

375

 

 

Bt. path

+3

0

-3

-5.3

-8.3

-11.8

 

3

Yards

100

264

302

325

350

375

400

 

Bt. path

+3

0

-3

-5.2

-8.1

-11.5

-15.2

4

Yards

100

260

299

325

350

375

400

 

Bt. path

+3

0

-3

-5.6

-8.5

-11.9

-15.7

5

Yards

100

202

234

250

 

 

 

 

Bt. path

+2

0

-2

-3.2

 

 

 


Sight height 1.6” (Scope).

 

No

At yards

10mphXwind

Velocity

Ft-lb’s

1

300

8.1

2133

3031

2

300

9.7

2186

2492

3

300

8.2

2259

2833

4

300

7

2281

3119

5

200

3.7

2291

3497

 

Wind value (very) roughly doubles at 400 yards.

375 Weatherby final

.375 WBY

Imperial

Metric

A

.532

13.5

B

.513

13.03

C

15 deg

 

D

.450

11.43

E

.402

10.21

F

2.412

61.27

G

.438

11.13

H

2.850

72.4

Max Case

2.850

72.4

Trim length

2.840

72.1

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